Deisi

The Déisi were a class of peoples in ancient and medieval Ireland. The term is Old Irish, and derives from the word déis, meaning "vassal" or "subject"; in its original sense, it designated groups who were vassals or rent-payers to a landowner. Later, it became a proper name for certain septs and their own subjects throughout Ireland. The various peoples listed under the heading déis shared the same status in Gaelic Ireland, and had little or no actual kinship, though they were often thought of as genetically related. Déisi groups included the Déisi Muman (the Déisi of Munster), Déisi Temro (of Tara), Déisi Becc (located in the Kingdom of Mide) and the Déisi Tuisceart (the Northern Déisi; a sept of which would become famous as the Dál gCais). During the Early Middle Ages some Déisi groups and subgroups exerted great political influence in various parts of Ireland, and certain written sources suggest a connection to Britain as well.

The early histories of the Déisi groups are obscure. As a class that evolved from peoples tied by social status rather than kinship, groups had largely independent histories in different parts of Ireland. While some medieval texts attempt to give the Déisi an aristocratic origin, these are later fabrications dating to the period after the Déisi had gained political power. Despite their tributary origins, representatives of at least one Déisi population would eventually achieve spectacular success, founding a powerful medieval dynasty which is still in existence.

The Déisi Muman were a prominent enough power to form their own regional kingdom in Munster from a fairly early date. In a recent title, Paul MacCotter states "The regional kingdom of Déisi Muman must have existed in roughly its present location from a very early period. Oghams dating perhaps from the fifth century record unique first names associated with its kings." According to Francis John Byrne, there are certain inscriptional hints that both the Eóganachta and their Waterford Déisi vassals may have been of fairly recent Gaulish origins. The ancestors of the Eóganachta are known as the Deirgtine and they are also believed to have been active in Roman Britain, one piece of evidence being the name of their capital Cashel, thought to be inspired by the Roman castella they observed on raids. The Déisi Muman enjoyed a position in the later Eóganachta overkingdom suggesting of a special relationship. Byrne mentions it was noticed by Eoin MacNeill that a number of the early names in the Eóganachta pedigrees are found in oghams in the Déisi country of Waterford, among them Nia Segamain (NETASEGAMONAS), after the Gaulish war god Segomo. According to MacNeill, the Waterford Déisi and the Eóganachta at Cashel "cannot well be disconnected".

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